Question: Tiffany has biked her bike for a total of $21$ miles since she started biking daily. She has been biking $3$ miles each day. For how many days has Tiffany been biking?
Answer: The number of days that Tiffany has been biking is the total number of miles biked divided by the number of miles biked each day. $21\text{ miles} \div 3\text{ miles per day} = \text{number of days biking}$ $21\text{ miles} \div 3\text{ miles per day} = 7\text{ days}$